Device for recording with electron rays

ABSTRACT

A device is disclosed for recording image elements, by exposing recording material, at constant current density with the aid of a focused electron beam provided with means before the last focusing device for varying the shape and/or size, in the recording plane, the cross section of the electron beam in conformity with image signals.

United States Patent Le Poole et al.

[451 Jan. 25, 1972 DEVICE FOR RECORDING WITH ELECTRON RAYS Inventors:Jan B. Le Poole, Delft; Leendert A. Fontijn, Maasdijk; Alfred B.BoIQBerkel, all of Netherlands Assignee: Nederlands Centrale Organisatievoor Toegepast-Natuurwetenschappelijk Onderzoek, The Hague, NetherlandsFiled: May 26, 1969 App1.No.: 827,510

Foreign Application Priority Data May 27, 1968 Netherlands ..6807439 US.Cl ..346/74 EB, 178/6.6 B, 178/6.7 R, 219/121 EB, 346/74 ES, 346/74 CRInt. Cl ..B23k l5/00,G01d 15/04, G1 1c 13/00 Field of Search ..346/74EB, 74 ES, 74 CR;

328/123, 124; 219/121 EB; 178/6.7 R, 6.6 B

[561 References Cited UN lTED STATES PATENTS 3,113,896 12/1963 Mann.346/74 3,118,050 1/1964 Hetherington. ...219/1l7 3,371,190 2/1968 Meyer..219/220 3,491,236 1/1970 Newberry ..346/74 Primary Examiner1*loward W.Britton AttorneyWatson, Cole, Grindle & Watson [57] ABSTRACT A device isdisclosed for recording image elements, by exposing recording material,at constant current density with the aid of a focused electron beamprovided with means before the last focusing device for varying theshape and/or size, in the recording plane, the cross section of theelectron beam in conformity with image signals.

13 Claims, 11 Drawing Figures BIPRISM (MODULATION SYSTEM 1 PATEMEBmzsmz3638.231

SHEET 1 0F 5 QUADRUPOLE LENS SYSTEMS FIG.2

NORTH POLE COIL SOUTH SOUTH POLE COIL POLE COIL QUADRUPOLE LENS SYSTEMNORTH POLE COIL FIG.3

NORTH POLE COILS RESISTANCE RESISTANCES wm-l TH 11 $1.: oms CONTACTSPOLE COILS PATENIEnmzsmz 3.838.231

SHEET 2. OF 5 ELECTRON SOURCE 19 f (BIPRISM ELECTROSTATIC 1g MODULATIONBIPRISM q 2 SYSTEM) QUADRUPOLE DIAPHRAGM a 4 CLU2ADRUPOLE DIAPHRAGM-PATENTEDJAH25IBY2 3338.231

B ELECTRON tY-J SOURCE SLIT LENS SLIT LENS INVENTORJ y 4 7% DEVICE FORRECORDING WITH ELECTRON RAYS The invention relates to a device forbinary recording with the aid of an electron beam provided with anelectron source for producing the beam, a means for focusing the beam,electron optical means for shaping the beam and for exposing therecording material with the beam at virtually constant current densityand means for displacing the recording material and the beam relativelyto each other.

Similar devices are known. n the one hand devices are known for exposinga photographic emulsion or a photolacquer for making a mask. On theother hand arrangements are known for exposing a photographic emulsionor photolacquer for carrying out direct processes on circuits.

In the case of the device for making a mask, the mask to be made is areduced image of a material mask previously placed between the condenserlens and the intermediate lens. If, therefore it is desired to makemasks of a different shape, the material mask must be replaced by amaterial mask of that shape. In the case of the device for carrying outprocesses on circuits, the processes are guided by a computer controltape. During the exposure the beam is focused on the workpiece and thenalways has practically the same shape and cross section. The requiredpattern is produced by deflecting the focused beam.

It is the object of the invention to provide a different method ofmaking a pattern, which has proved to have many additional advantages.

For this purpose, the invention is characterized by means of varying theshape and/or size of the cross section of the electron beam in therecording plane, formingthe exposing part in an image element.

The required pattern is produced by dividing this pattern into imageelements and by making exposures in these elev ments with the beam, witha beam cross section varying locally in size and shape, the beam beingcontrolled for this by a programmed computer or by a scanned model.

In one embodiment the electron beam cross section is controlled by abiprism placed between the electron source and the focusing device, thebiprism being an electrostatic prism across which the voltagedifferential can be modulated.

Application of this control system results in two point focuses of thesource at each side of the original focus, each having half theintensity and the distance between them being proportional to themodulation. By applying two quadrupole lenses in succession in thedirection of the beam, the point focuses are changed into line focuses.Such a system with line focuses and a diaphragm located before therecording plane is particularly suitable for use in binary recording.

In another embodiment the electron beam cross section is controlled bymodulation of a deflecting device located between a diaphragm and afocusing device with a second diaphragm aligned with the first diaphragmand located in the image plane of this focusing device.

The means used in this embodiment are applied instead of and in theplace of the biprism mentioned in the first embodiment.

The invention will be further elucidated by reference to a drawing withnine figures for these and other embodiments and details.

FIG. 1 shows the path of the beam when imaging with two quadrupolelenses.

FIG. 2 shows a quadrupole lens diagrammatically. FIG. 3 shows a circuitfor feeding a quadrupole lens.

FIG. 4 shows a biprism.

FIG. 5 is a sketch showing the principle of the path of the beam in anexposure apparatus with a biprism and quadrupole lenses.

FIG. 6 shows a slightly different beam path diagrammatically in' asingle plane and with means added for inverting the exposed image.

FIG. 7 shows the beam path for an apparatus in which the means comprisetwo half diaphragms, a deflector and a focusing device.

FIGS. 7a and 7b show the operation of the regulated deflecting system Iin FIG. 7.

FIG. 8 shows three embodiments of diaphragms applicable in apparatuswith a beam as in FIG. 7.

FIG. 9 shows an exposure apparatus'in perspective.

In the figures, identical numbers and letters relate toidenticalelements.

FIG. 1 shows three rays, 1, 2 and 3 of a diverging beam transmitted bysource B and converging at point C.

Rays 1 and 3 and rays 2 and 3 are in planes which are at an angle ofLines A and A, show diagrammatically the strength of the quadrupolelenses and the quadrupole lenses themselves, which provide the image Cof source B.

The arrows 4, 5, 6 and 7 in lines A, and A indicate the direction offocusing and defocusing of the beam.

Arrow 4, for instance, indicates that the beam in the plane of rays 2and 3 is further diverged by the first lens and arrow 5 indicates thatthe beam in the plane of rays 1 and 3 is converged by the first lens.

The quadrupole lenses A, and A therefore focus in one plane and hencedefocus in the plane practically perpendicular thereto.

Each quadrupole lens A, and A consists of four coils 8, 9, l0 and 11,see FIG. 2, designed separately.

The strength of the lens is calculated from the imaging and enlargingrequirements and is determined by the column dimensions.

The current through a coil 8, 9, l0 and ll of the lens is determinedwith the aid of the formulas:

1 B sine [3.1 and fry-"B sine in which ni the number of ampere windingsper coil.

u the accelerating potential of the electrons in volts.

1 the length of the coil parallel to the system axis.

r= the distance from the coil to the axis.

The circuit for the coils of a lens is shown in FIG. 3.

In order to correct the first order deflection fault, both north andsouth poles are included in a simple balanced circuit. The location ofthe two lenses follows from the imaging and enlarging requirements.

In the embodiment of an exposure installation shown in FIG. 5 a biprismas shown in FIG. 4 is connected before the quadrupole lenses A, and AThe biprism consists of a hollow cylinder 15 and a tungsten wire 16.

The cylinder 15 is provided with an opening 17 to let through-beam 19and an opening 18 to let through beams l9 and 19 Beams l9, and 19, areobtained by applying a voltage differential across the biprism.

In this way, two virtual sources arise and, depending upon the voltagedifferential, these virtual sources will either overlap or not.

Owing to a slit diaphragm being applied as a Wehnelt opening in theelectron source of FIG. 5, anelliptical crossover of the source isobtained.

The ratio between the two main axes is then about 1:3, which is animprovement on the customary case with a round Wehnelt opening, in whichthe ratio may be as high as 2:3.

Theline source B so obtained forms, with the aid of the biprism of whichonly wire 16 is shown, two virtual line sources B and B for thequadrupole lenses A, and A, which image the sources B and B at C and Con coated roll 20.

Images C, and C consist of line images about 100 microns Coated rollrotates at a constant speed under images C,

and 0,, moving axially at the rate of 0.14 mm. per rotation.

Because of the 0.14-mm. pitch of coated roll 20 and the track therebydescribed on roll 20 of the line images C and C a 0.15-mm. diaphragm Dis applied immediately above roll 20 to prevent the tracks overlapping.

Owing to the presence of diaphragm D the cross section of the electronbeam in the recording plane is varied owing to modulation on roll 20 asshown (See exposed tracks E).

To limit the margin of error in imaging due to lens aberrations,especially owing to spherical aberration, the beam is diaphragmedthrough diaphragm D The exposed coated roll 20 can if desired begravured by etching, the unexposed parts being etched after developmentof the KPR. coating, each image element of a form thus containing forinstance one or more ink cells with different surface areas and/ordifferent depths. I

FIG. 6 shows diagrammatically the path of the beam for a device withinverted line imaging.

In this device the biprism 16 is located after the first quadrupole lensA, in order to increase sensitivity. In the absence of modulation ofbiprism 16, images C, and C coincide on mask F. There is then noexposure on the coated roll 20.

Upon modulation, images C, and C fall partly or entirely outside mask F.

The second biprism G and the rotational-symmetric lens H combine theseimages C and C again to a line image I, whose length is determined bymodulation and with which coated roll 20 is exposed.

FIG. 7 shows the path of the beam, again in a different arrangement.

Source B is imaged by the rotational-symmetric lens K in the plane ofthe rotational-symmetric lens N.

A diaphragm L, embodiments of which are drawn in FIG. 8, intercepts partof the beam.

A deflection system M, to which a modulating signal can be connected islocated before lens N.

Behind lens N, there is a diaphragm O.

In the absence of modulation of system M, the image in the plane of lensN will be imaged unimpeded through diaphragm O on roll 20, with the aidof the rotational-symmetric lens H.

The continuous lines converging in image element R show the path of thebeam in this situation.

If the system M is modulated, however, part of the beam will beintercepted by diaphragm O.

The broken lines converging in image element R show the path of the beamfor this.

Deflection system P is coupled to system M and is applied to ensure thatthe centers of gravity of the image elements are aligned on thecylinder.

FIG. 7a gives an example of this for line image elements in the absenceof deflection system P.

FIG. 7b gives an example of image elements in the form of squares, inwhich, with the regulated system P, for example, the centers of gravityare shown on a straight line 2.

Upon application in FIG. 7 of a diaphragm L, O of the type shown in FIG.8a, image elements R are obtained in the form of a line whose lengthvaries with modulation.

Upon application of a diaphragm of the type shown in FIG.

812, these become squares whose size varies with modulation. And uponapplication of a diaphragm of the type shown in FIG. the image elementsform a squared pattern with a constant number of squares varying in sizewith modulation.

FIG. 9 shows diagrammatically and in perspective an arrangementaccording to the invention with a beam path corresponding to that ofFIG. 6 using slit lenses S and T instead of the quadrupole lenses A, andA The modulating signal can, of course, be adapted electronically to thestandards required for good reproduction of the halftones in theresulting print.

This is very important because the signal of the device scanning theoriginal will not be linear with the quantity of ink which must betransferred per ink cell from the printing cylinder to the copy.

With this system, local corrections are of course also possible.

We claim:

1. A device for binary recording with the aid of an electron beamcomprising an electron source for producing said electron beam, arecording medium, a means for focusing the central axis of said beam onsaid recording medium, electron opti cal means for shaping said beam andfor exposing said recording medium with said beam, means for displacingsaid recording medium and said beam relatively to each other, and meansfor varying the cross section of said electron beam on said recordingmedium with respect to said central axis to form an image thereon atsubstantially constant current density.

2. A device as claimed in claim 1 further comprising two electrostaticslit lenses located in succession in the direction 'of said beam fromsaid electron source to said recording medi- 3. A device as claimed inclaim 1 wherein said electron source includes a slit diaphragm.

4. A device as claimed in claim 1 further comprising a diaphragm locatedin front of said recording medium.

5. A device as claimed in claim 1, wherein said means for varying thecross section of the beam comprises a biprism located to intersect saidbeam and a modulator for controlling said biprism to deflect said beam.

6. A device as claimed in claim 5, wherein said means for varyingfurthermore includes in succession from said electron source to saidrecording image a mask located in the image plane of said means forfocusing, a second biprism, and a second focusing means.

7. A device as claimed in claim 5, wherein said biprism is anelectrostatic prism in the form of a cylindrical condenser with an innerconductor, and said modulator modulates the voltage differential acrosssaid inner conductor.

8. A device as claimed in claim 1 further comprising two quadrupolelenses located in succession in the direction of said beam from saidelectron source to said recording medi- 9. A device as claimed in claim8, wherein said quadrupole lenses are magnetic lenses and furthercomprising means for rotating and axially displacingsaid quadrupolelenses with respect to the central axis of said beam.

10. A device as claimed in claim 8 further comprising a diaphragmlocated in the principal plane of one of said quadrupole lenses.

11. A device as claimed in claim 1, wherein said means for varying thecross section of said beam are located between said electron source andsaid means for focusing and comprise in succession from said electronsource tosaid recording medium a first diaphragm, a deflector, a secondfocusing means and a second diaphragm in alignment with said firstdiaphragm in the image plane of said second focusing means.

12. A device as claimed in claim 11, wherein the diaphragms are segmentsof a circle.

13. A device as claimed in claim 11, wherein the diaphragms are gauzes.

1. A device for binary recording with the aid of an electron beamcomprising an electron source for producing said electron beam, arecording medium, a means for focusing the central axis of said beam onsaid recording medium, electron optical means for shaping said beam andfor exposing said recording medium with said beam, means for displacingsaid recording medium and said beam relatively to each other, and meansfor varying the cross section of said electron beam on said recordingmedium with respect to said central axis to form an image thereon atsubstantially constant current density.
 2. A device as claimed in claim1 further comprising two electrostatic slit lenses located in successionin the direction of said beam from said electron source to saidrecording medium.
 3. A device as claimed in claim 1 wherein saidelectron source includes a slit diaphragm.
 4. A device as claimed inclaim 1 further comprising a diaphragm located in front of saidrecording medium.
 5. A device as claimed in claim 1, wherein said meansfor varying the cross section of the beam comprises a biprism located tointersect said beam and a modulator for controlling said biprism todeflect said beam.
 6. A device as claimed in claim 5, wherein said meansfor varying furthermore includes in succession from said electron sourceto said recording image a mask located in the image plane of said meansfor focusing, a second biprism, and a second focusing means.
 7. A deviceas claimed in claim 5, wherein said biprism is an electrostatic prism inthe form of a cylindrical condenser with an inner conductor, and saidmodulator modulates the voltage differential across said innerconductor.
 8. A device as claimed in claim 1 further comprising twoquadrupole lenses located in succession in the direction of said beamfrom said electron source to said recording medium.
 9. A device asclaimed in claim 8, wherein said quadrupole lenses are magnetic lensesand further comprising means for rotating and axially displacing saidquadrupole lenses with respect to the central axis of said beam.
 10. Adevice as claimed in claim 8 further comprising a diaphragm located inthe principal plane of one of said quadrupole lenses.
 11. A device asclaimed in claim 1, wherein said means for varying the cross section ofsaid beam are located between said electron source and said means forfocusing and comprise in succession from said electron source to saidrecording medium a first diaphragm, a deflector, a second focusing meansand a second diaphragm In alignment with said first diaphragm in theimage plane of said second focusing means.
 12. A device as claimed inclaim 11, wherein the diaphragms are segments of a circle.
 13. A deviceas claimed in claim 11, wherein the diaphragms are gauzes.